AHCI : Enable in Windows 7 / Vista

Windows will NOT install unless the bios has the sata drives as ide, no problem installing windows that way, but as soon as bios has sata drives as achi, windows 7 will not install to any drive whatsoever it says unable to install to so and so drive, have had one drive connected to sata port 1-6 and each time the same message came up...so to reiterate, Windows will not install if in the bios anything but ide is chosen to have the ports as. Windows wont even recognize any drivers that you can load before installing the system to, have tried the proper drivers(load drivers option before installing windows 7) and the same thing comes up. It might be the motherboard that I am using(m3n72-d asus) which is windows 7 compatible, but I have not read much more about the trouble I am having. Not many use 6 sata devices I guess.

Please excuse me if I seem a bit terse. I have been working on this problem for about a week now trying different things and no I dont think that I have tried everything(obviously) but I have tried many things many ways to no avail.
Any suggestions will be welcomed since I am at a loss as to why. Until then will have to hit f8 at bootup to get to the load manager to load the correct drive with windows on it

Thankyou for the suggestion, but as the saying goes-been there done that

Had the same issue but once I did a clean install and diskpart then force my Asus F1 to boot off that drive, windows boot up properly and has been since then. Again, did have to force/chose the ssd drive to boot off from. Now I did not have any problems installing W7 in ahci mode, just had to install the drives afterwards but it did install, that is weird that it won't on yours.

I have tried to do a low level format on the drive, connecting it as the only drive to sata port 1 with ahci enabled and windows 7 would not install to the hard disk, even though it was listed there as a drive, it just says windows cannot be installed to this hard drive. The only way I can install windows 7 is to put it back to ide mode in bios instead of ahci and install windows that way. Even with trying to install windows and using the correct drivers for my motherboard it will not install. Even now after installing windows 7 and putting the correct drivers in and enabling ahci in the bios(it already was after installing drivers and rebooting and so on)the drives were recognized fine(i changed the bios from ide to ahci) and it booted up fine and installed the necessary ports and all. As soon as I turn off the computer and on again, I have to do the f8 thing to boot to the right drive. As stated before even using easybcd which will go into the boot manager and tell you what drive and so on, everything is fine by that program. I am at a loss as to why windows wont boot to the correct drive-i have tried fixing it from the windows disc and I havent a clue what is going on.

Then I would get in touch with ASUS since mine is also Asus and works but again; did go into Bios and force to boot off the SSD drive which has W7 on it but that was only on the first time, once force, Asus save the settings and is now booting W7. Sounds to me like there's something in the Bios not set up correctly since W7 does not determine which drive to boot off, BIOS does.

i have a question what exactly does enableing this do? never heard of it but im wondering what it does and how does it benfit the system?